The present invention relates to a switch that cuts the circuit by using a bimetallic plate when overload and no fuse or breaker is required.
A conventional switch known to applicant is disclosed in FIGS. 1 and 2 and generally includes a base 1 with two terminals 7 and a conductive plate 27. The two terminals 7 each have a first contact point 9 and the conductive plate 27 has two second contact points 271 which are lowered to contact the first contact points 9 by pushing a button assembly 25. A first spring 11 is biased between the inside of the base 1 and the conductive plate 27 and a second spring 23 is biased between the button assembly 25 and the conductive plate 27, wherein the first spring 11 has a larger spring force than the second spring 23 so that the conductive plate 27 is located at a position as shown in FIG. 1. When pushing the button 252 of the button assembly 25, the conductive plate 27 is lowered and the second contact points 271 contact the first contact points 9 as shown in FIG. 2. The conductive plate 27 is raised by the first spring 11 when the button 252 is pushed again and released by the operation of the mechanism of the button assembly 25. This switch cannot respond when the current overflows so that many safety switches are developed, such as U.S. Pat. Nos. 5,786,742, 5,223,813, 4,937,548, 4,661,667, 5,223,813, 4,931,762, 5,451,729, and 4,704,594. A common shortcoming of the safety switches is that there is a complicated mechanism involved in each base and most of them is suffered by a problem of delay response.
Therefore, it is desired to have a safety switch that requires only a simple structure which responses the current overflow so as to cut off the circuit.
In accordance with an aspect of the present invention, there is provided a safety switch that comprises a base having two terminals and each terminal has a first contact point. A bimetallic plate is movably received in the base and two second contact points are connected to two ends of the bimetallic plate. The two second contact points are located above the two first contact points and the two ends of the bimetallic plate can be bent when overflow. A first spring is biased between an inside of the base and the bimetallic plate. A button assembly is connected to the base and a second spring is biased between the button assembly and the bimetallic plate. The two second contact points on the metallic plate are removed from the first contact points when the metallic plate is bent.
The present invention will become more obvious from the following description when taken in connection with the accompanying drawings, which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention.